1. Field of the Invention
The invention relates to a technology of measuring consumed electric energy in an image forming apparatus that operates in a plurality of different operation states such as a standby mode and an electric power saving mode.
2. Description of the Related Art
In recent years, there has been a demand for reduction in electric power consumption of electrical apparatuses in response to a request for energy saving. Against the backdrop of this movement, Japanese Patent Application Laid-Open No. 2007-295433 discloses an image forming apparatus in which electric energy information is generated by sampling actually measured values of electric power consumption in a predetermined cycle for each operation mode of the image forming apparatus, and the generated electric energy information is presented to a user. Accordingly, the user can be notified of electric power consumption and total electric power for each operation mode of the image forming apparatus, which can raise the user's awareness of energy saving.
However, conventionally, even in a sleep mode in which a fixing device requiring the largest electric power in the image forming apparatus stops its operation and therefore almost no fluctuation occurs in electric power consumption, actually measured values of the electric power consumption have been sampled in a predetermined cycle similarly to the other operation modes which cause a large fluctuation in electric power consumption. Therefore, the number of sampling times becomes excessively large in the sleep mode, resulting in an excessive amount of processing. Consequently, unnecessary electric power is consumed accordingly.